Imaging acoustic radiation forces and streaming with an optical trap

"We use ultrasonic fluid cavity resonances for the handling of beads, cells, living organisms and droplets inside microfluidic devices. This technology on lab-on-a-chip systems had an increasing number of applications in micro biology and medical research in the last couple of years. The talk will give an overview about the field of applications of acoustofluidic devices and show a summery about our experimental research activities during the last years. It will include the controlled acoustic handling of fluid droplets and C. elegans organisms, as well as micro robotic tools and acoustic traps. The focus will be on a method for the direct measurement of the acoustic radiation and streaming forces on a micro-particle. This measurement method is based on a calibrated high gradient optical trap and a fully automated process control. We optically trap a silica micro-particle and we measure its relative displacement inside the optical potential well, due to acoustic forces generated by a harmonic excitation of the fluid domain. This procedure allows us to analyse the acoustic force fields inside the fluid domains of acoustofluidic devices. The measured forces are used to evaluate the environmental influences on the acoustic boundary, which are so far inaccessible in the device design and we can close therefore the characterization gap between ideal simulated and real fabricated devices."